Complete response with trastuzumab in heavily pretreated HER2-positive metastatic salivary duct carcinoma

Salivary duct carcinoma (SDC), an aggressive and relatively rare tumor, accounts for approximately 10% of all salivary gland malignancies. We report a case of a patient with a metastatic, human epidermal growth factor receptor 2 (HER2)-positive parotid SDC efficiently treated with docetaxel and trastuzumab combination after multiple series of chemotherapies. A 61-year-old man presented with SDC. After adjuvant radiotherapy, imaging revealed multiple metastatic lesions in the lungs. Systemic treatment with carboplatin and paclitaxel was initiated. After disease progression, doxorubicin, vinorelbine, and capecitabine were performed. Neurotrophic tropomyosin receptor kinase and AR (androgen receptor) were negative. Immunohistochemistry determined a HER2-positive score of 3. After multiple chemotherapy, the patient was started with combination of docetaxel and trastuzumab. A complete response was obtained after 3 months of treatment in the patient. In conclusion, SDCs are highly aggressive malignant tumors. Targeted therapy with trastuzumab targeting HER2 overexpression is a reasonable option in metastatic settings.